This invention relates to a dry distillation process for treating bituminous or oil-containing fine-grained material, particularly tar sand, with a heat carrier made of fine-grained dry distillation residue which is heated in a pneumatic conveyor line by hot combustion gases and then fed to a collecting vessel and mixed in a dry distillation zone with the fine-grained material to be subjected to dry distillation.
Dry distillation processes are known, e.g., from German Pat. Nos. 1,809,874 and 1,909,263 and U.S. Pat. Nos. 3,655,518 and 3,703,442. The materials to be subjected to dry distillation may consist, e.g., of tar sand, oil shale or bituminous marl. The heat carrier is usually distillation residue or a granular additional material. To ensure a high yield of oil, it has been suggested to use temperatures of about 450.degree.-650.degree. C for dry distillation to select temperatures of about 600.degree.-700.degree. C for the hot heat carrier. The dry distillation residue is usually not processed further.
When the feedstocks and/or fuels contain sulfur, the known processes involve a production of exhaust gases which may contain sulfur compounds, particularly SO.sub.2, in considerable amounts. Whereas processes known per se may be used to purify and desulfurize these exhaust gases, these known processes involve a considerable expenditure so that the costs of the plant are appreciably increased.